DE102021128879A1 - Internal gear pump with a pressure chamber and a pump unit - Google Patents

Abstract

The invention relates to an internal gear pump (1) and a pump unit. The internal gear pump (1) comprises a pump housing (8), an outer rotor (3) which is mounted in a receptacle (7) of the pump housing (8), an inner rotor (2) which is arranged in the outer rotor (3), and a Pressure chamber (20), which is formed between the receptacle (7) and an outer wall of the outer rotor (3) and is fluidically connected to a pressure side of the internal gear pump (1), the pressure chamber (20) being between two Seals (22) which are effective between the seat (7) and the outer rotor (3). The pump unit includes the internal gear pump (1) and an electric motor (6) that drives it.

Description

The invention relates to an internal gear pump with a pressure chamber between the receptacle of the outer rotor and the outer wall of the outer rotor. The invention also relates to a pump unit comprising an internal gear pump and an electric motor.

Internal gear pumps are well known. Exemplary representatives are annular gear pumps, also called gerotor pumps. They have an outer rotor and an inner rotor arranged inside the outer rotor. The outer rotor has a number of recesses which is usually 1 greater than the number of projections of the inner rotor. Therefore, when the inner rotor rolls inside the outer rotor, pumping chambers with changing volumes result.

A suction opening and a discharge opening for the fluid to be pumped are provided in the housing of the internal gear pump. The fluid is sucked in via the suction opening from the pumping chamber, the volume of which increases. The fluid is ejected from the delivery chamber, the volume of which is reduced, through the ejection opening.

For a high efficiency of the internal gear pump, it is important that the overflow losses between the inner rotor and the outer rotor are as small as possible. At the same time, such tolerances must be provided that the inner rotor cannot jam within the outer rotor over the entire temperature range in which the internal gear pump is to be used.

In order to ensure that the outer rotor touches the inner rotor on the pressure side (and thus the overflow losses are reduced), the DE 10 2019 100 158 A1 a gerotor pump is known in which the receptacle for the outer rotor is provided with a plurality of pockets which are fluidically connected to the fluid to be pumped. The pressure fluid present in the pockets during operation acts on the outer rotor in a defined direction, so that it rests against the inner rotor in a range that can be structurally adjusted by the position of the pockets.

The object of the invention is to provide an internal gear pump in which the external rotor can be better loaded against the internal rotor at a predetermined position.

The task is solved by an internal gear pump with a pump housing, an external rotor, an internal rotor and a pressure chamber. The outer rotor is mounted in a receptacle in the pump housing. The inner rotor is arranged in the outer rotor. The pressure chamber is formed between the receptacle and an outer wall of the outer rotor and is fluidically connected to a pressure side of the internal gear pump. The pressure chamber is delimited between two seals in the circumferential direction of the receptacle. The seals are effective between the seat and the outer rotor.

The internal gear pump can in particular be a gerotor pump.

Due to the seals, the pressure chamber is precisely defined in the circumferential direction, so that the direction of action of the pressure fluid present there during operation is also precisely defined. Furthermore, due to the seals that rest against the outer wall of the outer rotor, there are low flow losses, which contributes to a high degree of efficiency.

According to one embodiment, the seals are arranged in a floating manner in the pressure chamber. The seals are thus pressed against the outer rotor by the pressure in the pressure chamber, so that they can be optimally aligned independently of component-related tolerances. In addition, no mechanical configurations are necessary that act on the seals in the radial direction against the outer rotor.

The seals can be located in pockets of the pressure chamber formed by the wall of the receptacle. The pockets allow the seals to be easily positioned circumferentially. At the same time, the floating bearing can be implemented with little effort.

According to one configuration, at least one seal can be shorter in the radial direction than a depth of the pockets in the radial direction. As a result, there is a free space on the side of the seal facing away from the outer rotor, as a result of which the desired force can be exerted on the seal by the fluid located there in the case of a floating bearing, so that it is acted upon against the outer rotor.

If the seals are cuboid, inexpensive sealing strips or sealing strips can be used as the starting material, from which sections with the desired length can be cut off.

If a floating seal is not used, the seal can be elastically prestressed in the radial direction between a bottom of the respective pocket and the outer wall of the outer rotor be included. This ensures that, regardless of the pressure in the pressure chamber, the seal rests on the outer rotor and seals there, for example when the pump is started, when no pressure has yet built up in the pressure chamber.

When a seal elastically biased in the radial direction is used, the seal may be V-shaped in a section perpendicular to a rotation axis of the outer rotor. With the V-shape, the elastic prestressing force can be implemented in a particularly simple and cost-effective manner. Furthermore, when the apex of the V-shape is located on the side of the pressure chamber, the pressure in the pressure chamber causes the seal to be more tightly pressed against the outer rotor as the pressure increases.

Preferably, at least one support rib can be arranged in the pressure chamber between the seals, which protrudes radially inwards over adjacent wall sections of the receptacle. The support rib ensures that the outer rotor does not move excessively far out of its operating position when no pressure has yet built up in the pressure chamber. As soon as pressure has built up in the pressure chamber, the support rib has no function. In particular, it does not prevent the fluid from reaching the other side from one side of the pressure chamber via the support rib.

The supporting rib is preferably arranged in the circumferential direction in the pressure chamber symmetrically with respect to the seals of the pressure chamber, so that the position of the supporting force of the rib corresponds to the position of the hydraulic force from the pressure chamber.

The spacing of the seals in the circumferential direction determines the compressive force that is exerted on the outer rotor by the fluid in the pressure chamber during operation. The larger the distance, the larger the peripheral area of the outer rotor to which the pressure in the pressure chamber is exposed. This allows the contact force between the inner rotor and the outer rotor to be adjusted. The position of the seals relative to the suction and discharge ports determines the direction in which the compressive force acts. As a result, the contact force between the inner and outer rotor can be optimally adapted to the requirements or an optimal compromise can be set between different parameters. For example, a higher pressure force leads to lower overflow losses, but to higher friction and also to higher operating noise.

According to one embodiment of the invention, the pressure chamber is arranged in such a way that an angular range spanned by the pressure chamber in a cross-sectional area perpendicular to the axis of rotation of the outer rotor is between 15° and 150°, preferably between 25° and 130°, more preferably between 45° and 90° , also essentially 65°. The angular range is defined by the seals, since these delimit the pressure chamber on the circumference. The angular range that is expediently used to generate an appropriate compensating force generally depends on the number of recesses in the outer rotor and the number of teeth on the inner rotor. The angular range specified here can be used in particular for a configuration with an outer rotor with five recesses and an inner rotor with four teeth. The angular range can be adapted accordingly for other combinations of recesses and teeth, for example on the basis of FEM simulations.

Starting from a line of intersection perpendicular to the axis of rotation of the outer rotor, which divides the pressure chamber symmetrically, the seals consequently have an angular offset of ±7.5° to ±75° in relation to the line of intersection, preferably from ±12.5° to ±65°, more preferably from ±22.5° to ±45°, furthermore from essentially ±32.5° (relative to the intersection line).

The seals may be made of a material comprising polytetrafluoroethylene (PTFE) so that long life with low friction is obtained.

The inner rotor and/or the outer rotor can be made at least partially from an injection molding material, for example a plastic, so that the production costs are low.

Optionally, the internal gear pump can have a second pressure chamber. The second pressure chamber is also formed between the seat and the outer wall of the outer rotor, is fluidically connected to the pressure side of the internal gear pump and is delimited in the circumferential direction of the seat between two additional seals. The additional seals are effective between the receptacle and the outer rotor. The seals can be designed in particular as described above. The second pressure chamber can likewise be designed in accordance with the pressure chamber described above. For example, the second pressure chamber can also include a support rib. A pressure force can be generated with the second pressure chamber, which acts on the outer rotor in the desired direction in the event of rotation in the opposite direction.

Optionally, the second pressure chamber can be arranged as a mirror image of the first pressure chamber with respect to the outer rotor.

The object is also achieved by a pump unit that includes at least one internal gear pump as described above and an electric motor that drives the internal gear pump.

The invention and other advantageous embodiments and developments thereof are described and explained in more detail below with reference to the examples shown in the drawings. Show it:

• - 1 eine Draufsicht auf eine erfindungsgemäße Innenzahnradpumpe;
• - 2 eine Draufsicht auf die Innenzahnradpumpe von 1, wobei ein Teil des Gehäuses entfernt ist, um den Innenrotor und den Außenrotor sehen zu können;
• - 3 in vergrößertem Maßstab das Detail III von 2;
• - 4 das Detail von 3 in einer Ausführungsvariante;
• - 5 einen Schnitt entlang der Ebene V-V von 2;
• - 6 in vergrößertem Maßstab das Detail VI von 5;
• - 7 einen Schnitt entlang der Ebene VII-VII von 1;
• - 8 eine Ansicht entsprechend derjenigen von 2, wobei der Innenrotor und der Außenrotor entfernt sind;
• - 9 eine perspektivische Ansicht der Innenzahnradpumpe im Zustand von 8; und
• - 10 einen Schnitt entlang der Ebene X-X von 8.

The invention is described below with reference to an embodiment which is illustrated in the accompanying drawings. In these show:

• - 1 a plan view of an internal gear pump according to the invention;
• - 2 a plan view of the internal gear pump of 1 , with part of the housing removed to view the inner rotor and outer rotor;
• - 3 on an enlarged scale the detail III of 2 ;
• - 4 the detail of 3 in an embodiment variant;
• - 5 a section along the plane VV of 2 ;
• - 6 on an enlarged scale the detail VI of 5 ;
• - 7 a section along the plane VII-VII of 1 ;
• - 8th a view similar to that of 2 , with the inner rotor and the outer rotor removed;
• - 9 a perspective view of the internal gear pump in the state of 8th ; and
• - 10 a section along the plane XX of 8th .

In the figures, an internal gear pump 1 is shown, which has an inner rotor 2 and an outer rotor 3 . A gerotor pump is shown as an example representative of an internal gear pump 1.

In the exemplary embodiment shown, the inner rotor 2 has four teeth, which roll in an inner contour of the outer rotor 3, which has five recesses (and accordingly five projections lying in between). In this way, when the inner rotor rotates within the outer rotor, pumping chambers that are delimited from one another and whose volume changes arise. This functional principle is generally known for gerotor pumps.

The inner rotor 2 is mounted on a drive shaft 4 on which a rotor 5 of an electric motor 6 is attached. The electric motor 6 forms a pump unit together with the internal gear pump, here the gerotor pump.

The outer rotor 3 is accommodated in a receptacle 7 which is part of a pump housing 8 .

The receptacle 7 has an inner wall 9 that is mostly circular-cylindrical, the center point M of which is offset by a distance E from the central axis of the drive shaft 4 . During operation of the gerotor pump, the outer rotor 3 rotates about the central axis M (counterclockwise in the exemplary embodiment shown, based on 2 ).

The fluid to be pumped by the gerotor pump is drawn in via a suction opening 10 (see Fig 1 and 7 ) of the pumping chamber delimited between the inner rotor 2 and the outer rotor 3 on the suction side. The fluid is supplied from both sides of the inner rotor as viewed in the axial direction; part of the fluid passes through an overflow opening 12 (see Fig 1 , 2 , 8th and 10 ) into the area of the electric motor 6 and can be drawn from there via an opening 14 formed in the bottom of the pump housing (see in particular 8th ) to be sucked in.

The fluid sucked into a delivery chamber is conveyed from this to a pressure outlet 16 and ejected there from the delivery chamber, the volume of which decreases.

When the gerotor pump is operated, there is always a higher pressure on the pressure side within the pumping chambers than on the suction side. As a result, the outer rotor 3 relative to the inner rotor 2 approximately in the direction of the arrow P of 2 is applied. Since at the same time certain tolerances and gap dimensions would have to be present between the inner rotor 2 and the outer rotor 3 so that the inner rotor 2 cannot jam inside the outer rotor 3 or excessive friction occurs, the acting compressive force tends to close overflow gaps between the outer contour of the Inner rotor 2 and the inner contour of the outer rotor 3 to generate.

In order to counteract the acting compressive force (and the resulting displacement of the outer rotor 3 relative to the inner rotor 2), a pressure chamber 20 is delimited between the receptacle 7 and the outside of the outer rotor 3, which is filled with fluid during operation that is under delivery pressure.

The pressure chamber 20 extends in the circumferential direction between two seals 22 which seal between the inner wall of the receptacle 7 and the outer wall of the outer rotor 3 . The seals 22 extend in the axial direction over the entire height of the outer rotor 3.

Related to 2 the pressure chamber 20 thus extends here between a position at approximately 9:30 o'clock and a position at approximately 2 o'clock.

A recess 24 is provided in the bottom of the pump housing 8 and extends in the circumferential direction over the area in which the pumping chambers reduce their volume and eject the fluid to the pressure outlet 16 . The recess 24 has a radially outwardly extending branch channel 26, by means of which the pressure chamber 20 is connected to the recess 24 and thus to the delivery chambers. During operation, fluid is thus conducted to the pressure chamber 20 via the recess 24 and the branch channel 26 .

The seals 22 are each accommodated in a pocket 30 in the wall of the receptacle 7 . As in 3 As can be seen, the seal 22 has a V-shaped cross-section with the apex of the V facing the pressure chamber 20 .

Because of its shape, the seal 22 is held elastically prestressed between the bottom of the pocket 30 and the outer wall of the outer rotor 3 .

The seal 22 is accommodated in a floating manner in the pocket 30, the region of the pocket 30 which lies radially outside the apex of the seal 22 also being exposed to the pressure in the pressure chamber 20. A small widening 32 is provided on each pocket 30 for this purpose.

In 4 an embodiment variant is shown in which the seal 22' has a rectangular cross-section. The seal 22 ′ is also mounted in a floating manner in the embodiment variant, with the radially outer “rear side” of the seal 22 ′ being exposed to the pressurized fluid which is also present in the pressure chamber 20 via the widening 32 .

As in particular in 9 As can be seen, a support rib 36 is provided on the inside of the receptacle 7 within the pressure chamber 20, which ensures that when the pump starts up there is always a sufficient gap between the outside of the outer rotor 3 and the inner wall of the receptacle 7 in the area of the pressure chamber 20 , so that it can quickly fill with fluid.

During operation, the delivery pressure present within the pressure chamber 20 ensures that the outer rotor 3 is acted upon in the opposite direction of the arrow P and that the outer rotor 3 accordingly contacts the inner rotor 2 in the region of the delivery chambers which are under the delivery pressure. As a result, overflow losses between the inner rotor and the outer rotor can be reduced or almost completely prevented.

The amount of thrust force applied to the outer rotor 3 due to the fluid pressure of the pressure chamber 20 can be adjusted by the angular range over which the pressure chamber 20 extends, that is, the angular distance of the seals 22 from each other.

The force that acts in the direction of the arrow P due to the pressure conditions can be partially compensated, fully compensated, or even overcompensated, as desired.

The direction in which the pressure force exerted on the outer rotor 3 acts can be adjusted by the position of the two seals 22 relative to the suction port 10 and the pressure outlet 16 .

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102019100158 A1 [0005]

Claims (10)

Internal gear pump (1) with a pump housing (8), an outer rotor (3) which is mounted in a receptacle (7) of the pump housing (8), an inner rotor (2) which is arranged in the outer rotor (3), and a pressure chamber (20), which is formed between the receptacle (7) and an outer wall of the outer rotor (3) and is fluidically connected to a pressure side of the internal gear pump (1), the pressure chamber (20) being between two seals in the circumferential direction of the receptacle (7). (22) which are effective between the seat (7) and the external rotor (3). Internal gear pump (1) after claim 1 , wherein the seals (22) are arranged floating in the pressure chamber (20). Internal gear pump (1) according to one of the preceding claims, wherein the seals (22) are arranged in pockets (30) of the pressure chamber (20) which are formed by a wall of the receptacle (7). Internal gear pump (1) after claim 3 , wherein at least one seal (22) is shorter in the radial direction than a depth of the pockets (30) in the radial direction. Internal gear pump (1) according to one of the preceding claims, wherein the seals (22) are cuboid. Internal gear pump (1) after claim 3 , At least one seal (22) being elastically prestressed in the radial direction between a bottom of the respective pocket (30) and the outer wall of the outer rotor (3). Internal gear pump (1) after claim 6 , wherein the at least one seal (22) is V-shaped in a section perpendicular to an axis of rotation of the outer rotor (3). Internal gear pump (1) according to one of the preceding claims, wherein at least one support rib (36) is arranged in the pressure chamber (20) between the seals (22) and projects radially inwards over adjacent wall sections of the receptacle (7). Internal gear pump (1) according to one of the preceding claims, which has a second pressure chamber which is formed between the receptacle (7) and the outer wall of the outer rotor (3), is fluidically connected to the pressure side of the internal gear pump (1) and which, in the circumferential direction of the Housing (7) is delimited between two additional seals acting between housing (7) and external rotor (3). Pump unit comprising an internal gear pump (1) according to one of the preceding claims and an electric motor (6) which drives the internal gear pump (1).

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